Heretofore it has been known to make painting structures, such as paint spray booths, ovens or booth/ovens of rectangular or square cross-section or sometimes with a gable in the roof line to accommodate lighting fixtures. Prior art booths of these types can be seen in U.S. Pat. No. 4,220,078 and U.S. Pat. No. 4,222,319. These booths have filtered air emanating from the ceiling of the booth, then flowing into a work space below the ceiling, and thereafter, being drawn out from the bottom of the booth through a downdraft opening in the floor of the booth. While the air flow around the article being worked on, such as for example an automotive vehicle being painted, is excellent, the air flow provided to the workman may not always be ideal when the workman is, say, spraying the lower portion of the vehicle after having sprayed adjacent higher portions. The less than ideal air flow results as the solvents vaporizing off the higher painted portions may be carried to or close to the painter. Additionally, if this type of ceiling air flow is provided in an oven or a spray booth/oven, the temperature of the article may not be uniform as the upper portion of the article is closer to the source of the heat. Hence, the rate of paint solvent vaporization and drying may not be uniform over various portions of the article, and that can cause paint defects.
In another type booth shown in U.S. Pat. No. 4,133,255, the filtered air is similarly supplied from the ceiling of the booth, but is withdrawn from the work space beneath the ceiling by exhaust ducts set in the lower ends of the side walls of the booth, instead of through an opening in the center of the booth's floor. This construction is disadvantageous as it pulls the solvent ladden air to the side where the painter may be standing, and particularly when the painter is working down low on the vehicle. Further, if this type painting structure was also a hot air type booth/oven with heated air being supplied from the ceiling, the temperature of the painted article and, consequently, the paint solvent vaporization and paint drying rates would vary depending upon the distance from the ceiling.
U.S. Pat. No. 4,664,061 (FIG. 15) shows an automated spray booth with filtered air emanating from the ceiling and the lower portions of the booth's side walls. However, no air is discharged through the upper portions of the side walls. Thus, there are still some portions (where if a painter were present, the painter's head may spend considerable time), the upper outer portions of the booth, that are not purged as fully as other portions thereof. Further, while there may be air flow throughout the booth and around the article being painted, it is not uniform at all locations. Thus, if this type booth were used as hot air oven or booth/oven for drying paint, the temperature of the article in the oven, the painted surfaces and the rates of vaporization of solvents from the paint and of drying of the paint may not be as uniform as desired.